In a ceremony freighted with symbolism, Harvard University President Drew Faust lauded the Navy’s ROTC program and officially welcomed it onto campus yesterday, ending four decades of frosty relations between the university and the military and laying the groundwork for increased recruiting at the school. The event happened the same day the US government formally ended the “Don’t Ask, Don’t Tell’’ policy that barred gay and lesbian members of the military from openly acknowledging their sexuality. Harvard considered the policy discriminatory.